Process for making an aircraft having a floor

The invention relates to aircraft, and in particular to aircraft floors.

BACKGROUND OF THE INVENTION

When building an aircraft, it is known to begin by making a lower section of a segment of the fuselage. This lower section constituting the bottom portion of the segment is upwardly open. The portion of the floor that occupies this segment is then inserted through the upward opening. Thereafter, the various systems and members that are to be fastened to the fuselage and to the floor are mounted in the assembly. These may be hydraulic or pneumatic members (compressed air or air conditioning ducts, water ducts, refrigeration ducts, oxygen ducts), electric cables, fire extinguisher circuit elements, or indeed ducts for on-board communications networks. These various members are fastened to the underside of the floor or to the fuselage, e.g. in the zones referred to as “triangular” zones because of their shape, i.e. the zones that are close to the junction between the floor and the fuselage.

Nevertheless, that method of mounting presents drawbacks. Thus, it is necessary to wait until the structure (the fuselage and the floor) have finished being assembled before beginning to put the systems into place, thereby lengthening the overall time required to build the aircraft. Furthermore, introducing systems into the triangular zones raises ergonomic problems for operators. Those zones constitute a confined space that is of difficult access, obliging operators to work in crouching or even prone positions, particularly in fuselages of small diameter.

OBJECT AND SUMMARY OF THE INVENTION

An object of the invention is to accelerate and facilitate the building of the aircraft.

To this end, the invention provides a method of fabricating an aircraft, the method comprising the following steps: <ul><li id="ul0001-0001" num="0000"><ul><li id="ul0002-0001" num="0006">fastening two lateral floor portions, each firstly to a fuselage element and secondly to supports that are connected to the fuselage element; and then</li><li id="ul0002-0002" num="0007">bringing a middle floor portion between the lateral portions and connecting it to the lateral portions.</li></ul></li></ul>

Thus, the two lateral portions are mounted initially and the middle portion is mounted only subsequently. After the lateral portions have been mounted, it is possible to assemble systems in the triangular zones immediately, without waiting for the middle portion to be installed. Access thereto when the middle portion is absent becomes relatively easy and relatively ergonomic. In particular, operators can remain standing while they are installing systems. Furthermore, certain systems may be mounted on the middle portion of the floor before it is brought into the fuselage so as to be fastened to the lateral portions. Once more, conditions for mounting such systems are greatly improved, so far as the operators are concerned, since the middle portion is not yet installed in the fuselage. In addition, it is possible to assemble systems on the middle portion away from the main assembly line while the triangular zones of the fuselage are receiving the systems that are associated therewith. The corresponding operations can therefore be performed in parallel, thereby enabling the overall time required to build the aircraft to be reduced. Furthermore, the invention presents the advantage that the middle portion, which by definition has dimensions that are smaller than the overall dimensions of the floor, may be inserted even after the top portion of the fuselage segment has been secured to the bottom portion, thereby closing its top. Since the middle portion is of small size, it does not interfere with the frames while it is being inserted into a closed fuselage, and it is entirely possible to introduce the middle portion through the front or rear opening of the fuselage segment. In addition, the freedom thus provided for assembling the entire fuselage segment prior to inserting the middle portion of the floor makes the method of building the aircraft even more flexible, thereby also helping shorten the overall time required for assembly.

Advantageously, during the fastening step and before bringing in the middle portion, at least one member of the aircraft having a function other than a mechanical function for the floor or the fuselage is placed under the lateral portions.

Thus, advantage is taken of the absence of the middle portion, thereby making this operation more convenient.

Advantageously, prior to bringing in the middle portion, the middle portion is fitted with at least one member of the aircraft that has a function other than a mechanical function for the floor.

Likewise, advantage is taken of the fact that the middle portion is not yet installed in the fuselage, thereby making it easier to put the members into place.

In an implementation, top partial crossmembers are assembled with bottom partial crossmembers so as to form crossmembers of the middle portion, leaving at least one gap between the top partial crossmember and the bottom partial crossmember of each crossmember.

Thus, this arrangement does not significantly modify the mechanical properties of the crossmembers. In particular, each crossmember made up of top and bottom partial crossmembers presents substantially the same second moment of area as a conventional one-piece crossmember. This second moment of area comes from the relatively tall height that can be given to the crossmember made up of two partial crossmembers. In contrast, the gap available between the top and bottom partial crossmembers is useful for housing members such as those mentioned above, instead of placing them under the floor. This results in more space being made free under the floor. It is thus possible to increase the volume available for a cargo zone, or on the contrary, by lowering the floor, to increase the volume available in the cabin. It is also possible to take advantage of this greater compactness to reduce the total section of the fuselage. Conversely, for unchanging compactness, it is possible to increase the total height of the crossmembers of the floor so as to enable the floor to contain systems that are more voluminous than those that have been associated with the floor in the prior art. Furthermore, systems may be put into place between the partial crossmembers before they are connected together to constitute the crossmembers. This makes it much easier to install such systems, and in particular makes installing them more ergonomic for operators.

The invention also provides an aircraft that comprises: <ul><li id="ul0003-0001" num="0000"><ul><li id="ul0004-0001" num="0016">two lateral floor portions, each fastened both to the fuselage and to supports connected to the fuselage; and</li><li id="ul0004-0002" num="0017">a middle floor portion that is distinct from the lateral portions and that is connected to the lateral portions.</li></ul></li></ul>

The aircraft of the invention may also present at least any one of the following characteristics: <ul><li id="ul0005-0001" num="0000"><ul><li id="ul0006-0001" num="0019">the lateral portions are fastened to the middle portion by means of faces of the lateral and middle portions that are perpendicular to a longitudinal direction of the fuselage;</li><li id="ul0006-0002" num="0020">the lateral portions are fastened directly to the middle portion;</li><li id="ul0006-0003" num="0021">the lateral portions are fastened to the middle portion by means of faces of the lateral and middle portions that are horizontal;</li><li id="ul0006-0004" num="0022">the lateral portions are fastened to the middle portion with parts of the lateral and middle portions that are placed so as to extend one another;</li><li id="ul0006-0005" num="0023">the lateral portions are fastened to the middle portion with parts of the lateral and middle portions that are placed back to back;</li><li id="ul0006-0006" num="0024">the lateral portions are fastened to the middle portion via at least one connection part, e.g. by means of a rail;</li><li id="ul0006-0007" num="0025">the lateral portions are fastened to the middle portion using parts of the lateral and middle portions that are placed one inside another; and</li><li id="ul0006-0008" num="0026">the lateral portions are fastened to the middle portion by mutually superposing walls of the lateral and middle portions.</li></ul></li></ul>

In an embodiment, the middle portion includes crossmembers, each crossmember comprising a top partial crossmember and a bottom partial crossmember, with at least one gap being arranged between the top partial crossmember and the bottom partial crossmember of each crossmember.

Advantageously, the aircraft includes at least one row of passenger seats, the seats being associated with supports supporting respective seats in full, one of the seats being adjacent to an aisle, and the support of the seat that is adjacent to the aisle being connected to the fuselage and to the floor solely via the support of the seat that is adjacent thereto in the row.

Thus, at least one seat contiguous with the aisle is in a cantilevered arrangement. This means that the seats of the row bear against the floor at a greater distance away from the middle axis of the fuselage, thereby shortening the path via which loads are transmitted to the main structure of the fuselage and simplifying the design of the parts.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention appear further from the following description of embodiments given as non-limiting examples and with reference to the accompanying drawings, in which:

<figref idrefs="DRAWINGS">FIG. 1</figref> is a perspective view of an aircraft of the invention;

<figref idrefs="DRAWINGS">FIG. 2</figref> is a partially cutaway perspective view of a segment of the fuselage of the <figref idrefs="DRAWINGS">FIG. 1</figref> aircraft while receiving a middle floor portion;

<figref idrefs="DRAWINGS">FIGS. 3 and 4</figref> are views on a larger scale showing details of the <figref idrefs="DRAWINGS">FIG. 2</figref> structure;

<figref idrefs="DRAWINGS">FIG. 5</figref> is a fragmentary perspective view of one of the battens of the <figref idrefs="DRAWINGS">FIG. 2</figref> structure;

<figref idrefs="DRAWINGS">FIG. 6</figref> is a fragmentary perspective view showing a detail of how the <figref idrefs="DRAWINGS">FIG. 2</figref> floor is assembled;

<figref idrefs="DRAWINGS">FIG. 7</figref> is a face view of the elements of <figref idrefs="DRAWINGS">FIG. 6</figref>;

<figref idrefs="DRAWINGS">FIG. 8</figref> is a section view on plane VIII-VIII of the elements of <figref idrefs="DRAWINGS">FIG. 7</figref>;

<figref idrefs="DRAWINGS">FIG. 9</figref> is a view analogous to <figref idrefs="DRAWINGS">FIG. 3</figref> showing a second embodiment;

<figref idrefs="DRAWINGS">FIG. 10</figref> shows the elements of <figref idrefs="DRAWINGS">FIG. 9</figref> during assembly;

<figref idrefs="DRAWINGS">FIG. 11</figref> is a view on a larger scale showing a detail of the <figref idrefs="DRAWINGS">FIG. 9</figref> assembly;

<figref idrefs="DRAWINGS">FIG. 12</figref> is a view analogous to <figref idrefs="DRAWINGS">FIG. 3</figref> showing a third embodiment;

<figref idrefs="DRAWINGS">FIG. 13</figref> is a perspective view showing a detail of how the structure of the <figref idrefs="DRAWINGS">FIG. 12</figref> airplane is assembled;

<figref idrefs="DRAWINGS">FIGS. 14 and 15</figref> are respectively an elevation view and a side view of a portion of the <figref idrefs="DRAWINGS">FIG. 13</figref> assembly;

<figref idrefs="DRAWINGS">FIG. 16</figref> is a perspective view of the <figref idrefs="DRAWINGS">FIG. 13</figref> rail;

<figref idrefs="DRAWINGS">FIG. 17</figref> is a section view of an airplane fuselage in a fourth embodiment, in a plane perpendicular to the longitudinal direction of the fuselage;

<figref idrefs="DRAWINGS">FIG. 18</figref> is a fragmentary view on a larger scale of a portion of the <figref idrefs="DRAWINGS">FIG. 17</figref> fuselage;

<figref idrefs="DRAWINGS">FIG. 19</figref> is a perspective view of a portion of the <figref idrefs="DRAWINGS">FIG. 18</figref> fuselage;

<figref idrefs="DRAWINGS">FIG. 20</figref> is a section view on plane XX-XX of the <figref idrefs="DRAWINGS">FIG. 18</figref> crossmember;

<figref idrefs="DRAWINGS">FIG. 21</figref> is a view analogous to <figref idrefs="DRAWINGS">FIG. 20</figref>, showing a variant embodiment;

<figref idrefs="DRAWINGS">FIGS. 22 and 23</figref> are two perspective views showing how the middle portion of the floor is made and how it is inserted in the fuselage;

<figref idrefs="DRAWINGS">FIG. 24</figref> is a perspective view of the <figref idrefs="DRAWINGS">FIG. 17</figref> fuselage showing the seat supports; and

<figref idrefs="DRAWINGS">FIGS. 25 and 26</figref> are perspective views of the seat supports showing force diagrams for two configurations of applied stresses.

MORE DETAILED DESCRIPTION

With reference to <figref idrefs="DRAWINGS">FIG. 1</figref>, the aircraft <b>2</b> of the invention in the embodiment described below is constituted by an aerodyne, and specifically an airplane. The airplane <b>2</b> has a fuselage <b>4</b>, two wings <b>6</b>, a tail <b>8</b>, and engines <b>10</b>, specifically two engines fastened to the wings in this example.

An X, Y, and Z frame of reference is used below in which the direction X designates the longitudinal horizontal direction of the fuselage, the direction Y designates the horizontal direction perpendicular to the direction X, and the direction Z designates the vertical direction.

Over the major fraction of its length, the fuselage presents a generally cylindrical shape of axis parallel to the direction X, and of section that is generally circular in a plane perpendicular to said direction. A segment of the fuselage during assembly is shown in <figref idrefs="DRAWINGS">FIG. 2</figref>. The description below relates to this segment, it being understood that the fuselage may comprise a plurality of segments made up in the same manner and located one after another.

The fuselage <b>4</b> comprises mutually identical frames <b>12</b>. The frames <b>12</b> in this example are generally circular in shape, each extending in a vertical plane. The axes of the frames coincide with the longitudinal axis of the fuselage. The frames are mutually parallel, facing one another, and spaced apart from one another. The fuselage has a wall <b>14</b> of generally cylindrical shape fastened to the frames <b>12</b> by means of elements such as stringers <b>16</b>. Each stringer is in the form of a section member extending in the direction X and it is fastened via its outside face to an inside face of the wall <b>14</b>, while also being fastened via its inside face to the frame <b>12</b>. The stringers extend parallel to one another around the frame with which they are associated.

In a first embodiment, the segment contains a floor <b>18</b> comprising two lateral portions <b>18</b><i>l</i>, respectively left and right portions, and a middle portion <b>18</b><i>m</i>. The middle portion <b>18</b><i>m </i>extends between the lateral portions <b>18</b><i>l</i>. The overall shape of the floor <b>18</b> is generally that of a horizontal plane.

The middle portion <b>18</b><i>m </i>has crossmembers <b>20</b> formed by rectilinear section members extending in the direction Y. The crossmembers <b>20</b> are parallel to one another, facing one another, and spaced apart from one another. They all lie in the same plane. The middle portion <b>18</b><i>m </i>also has rails <b>22</b>, likewise formed by rectilinear section members extending parallel to one another, facing one another, and spaced apart from one another, but this time along the direction X. All of the rails <b>22</b> lie in the same plane. The rails are fastened to the crossmembers <b>20</b>, with the bases of the rails being in contact with the tops of the crossmembers.

With reference in particular to <figref idrefs="DRAWINGS">FIG. 3</figref>, which shows the left lateral portion, each of the lateral portions has section members formed in this example by battens <b>24</b>. The battens are in a disposition analogous to that of the crossmembers <b>20</b> of the middle portion. They thus extend in particular in the direction Y. They are disposed in such a manner as to come into contact with the corresponding ends of the respective crossmembers, as explained below. The inside end of each batten is rigidly fastened to the end of the corresponding crossmember. The outside end of each batten is rigidly fastened to the frame <b>12</b> where the batten is located. The inside end of each batten is also associated with a support such as a post <b>26</b> formed by a section member extending vertically. The top end of the post is rigidly fastened to a batten, while its bottom end is rigidly fastened to the same frame that is already fastened to the other end of the batten. The floor is made in such a manner that each frame <b>12</b> corresponds to a crossmember <b>20</b>, to two battens <b>24</b> respectively on the left and on the right, and two posts <b>26</b>, all of these parts extending substantially in the same plane perpendicular to the direction X.

In the present example, and as shown in <figref idrefs="DRAWINGS">FIG. 4</figref>, the bottom end of the post <b>26</b> is fastened to the frame <b>12</b> via a fastener <b>28</b> having a common face, specifically a front face, that comes into contact with a rear face of the post and with a rear face of the frame. The fastener <b>28</b> is rigidly fastened, e.g. by means of rivets, both to the post and to the frame.

With reference in particular to <figref idrefs="DRAWINGS">FIGS. 5 to 8</figref>, each batten <b>24</b> in the present example is a generally channel-section member. The inside end of the batten shown in <figref idrefs="DRAWINGS">FIG. 5</figref> is cut away by a recess <b>23</b> in its top edge, and over a short height of the top portion of the main wall of the section member. In the present example, the front face <b>30</b> of the web of the batten is in contact with a rear face of the frame <b>12</b> and these two parts are assembled together by means of rivets.

In this example, each crossmember <b>20</b> is likewise a channel-section member, however of smaller dimensions than the batten <b>24</b>, as can be seen in the section of <figref idrefs="DRAWINGS">FIG. 8</figref>. In the present reception, all three of the associated batten <b>24</b>, crossmember <b>20</b>, and post <b>26</b> overlap mutually as shown in <figref idrefs="DRAWINGS">FIG. 6</figref>. More precisely, three respective vertical walls of these three parts are superposed and in contact over an area, specifically, the wall of the batten is sandwiched between the wall of the crossmember and the wall of the post. These walls extend perpendicularly to the axis X. In the present embodiment, the channel-section of the crossmember is received inside the channel-section of the batten so that the outer front face of the crossmember lies against the inner rear face of the batten. The front face of the batten is in contact with the rear face of the post.

The assembly is made in such a manner that one of the rails <b>22</b> of the middle portion, the rail that is situated close to the edge of the middle portion, extends over the posts <b>26</b>, with this happening on both sides of the middle portion. The recess <b>23</b> made at the end of the batten enables it to extend under this rail.

The batten, the crossmember, and the post are rigidly fastened together by rivets, each passing through the three respective walls of these parts. Other rivets provide direct rigid fastening between the batten and the crossmember without passing through the post. As shown in <figref idrefs="DRAWINGS">FIG. 5</figref>, provision may be made for each end of each crossmember to present additional thickness in its junction zone with the associated batten, post, and rail, for reinforcing purposes. In this zone, the thickness E of the wall is thus greater than the thickness e of the remainder of the wall.

Fabrication of the airplane <b>4</b> comprises the following steps in particular.

The fuselage is made with the frames <b>12</b> and the wall <b>4</b>.

Then, inside the fuselage, the lateral portions <b>18</b><i>l </i>of the floor are installed. To do this, each lateral portion <b>18</b><i>l </i>is fastened firstly to the frames <b>12</b> of the fuselage, and secondly to the posts <b>26</b> that are themselves also connected to the fuselage. It should be observed that at this stage each of the left and right lateral portions does not constitute a single piece until it has been assembled with the fuselage.

After this assembly step, one or more members <b>70</b> of the airplane having a function other than a mechanical function for the floor or the fuselage is/are put into position under the lateral portions. By way of example, these members may be hydraulic or pneumatic (compressed air or air conditioning ducts, water ducts, refrigeration ducts, oxygen ducts), electric cables, fire extinguisher circuit elements, or indeed ducts of on-board communications networks.

In parallel with these operations (making the fuselage, installing the lateral portions, putting members into place), the middle portion <b>18</b><i>m </i>of the floor is made up by assembling the rails <b>22</b> with the crossmembers <b>20</b>. Prior to inserting the middle portion into the fuselage, the middle portion is fitted with at least one member <b>70</b> of the airplane that has a function other than a mechanical function for the floor, such as those mentioned above by way of example.

Finally, the middle portion <b>18</b><i>m </i>fitted out in this way is inserted into the fuselage segment and is connected to the left and right lateral portions <b>18</b><i>l </i>by being rigidly fastened thereto.

In this example, the fuselage segment also includes anti-crash connecting rods <b>34</b> of generally rectilinear and plane shape. Each connecting rod extends in a horizontal plane, but in a direction that is oblique relative to the directions X and Y. It has a rear end fastened to one of the stringers <b>16</b> of the fuselage. This stringer is rigidly fastened to a plurality of frames <b>12</b>, in this example it is fastened to four of them. The connecting rod <b>34</b> has its front end fastened to a rail <b>22</b> extending in the direction X and is itself rigidly fastened to a plurality of battens <b>24</b>. The connecting rods <b>34</b> situated in the left portion of the fuselage are coplanar and oriented in the same horizontal direction. The same applies to the connecting rods situated in the right portion of the fuselage. The connecting rods situated on the left are oriented towards the right, while the connecting rods situated on the right are oriented towards the left. Unlike the rails <b>22</b> of the middle portion, the rail <b>22</b> that is fastened to the connecting rods is not designed to receive passenger seats, and in this sense it is referred to as a “dummy rail”.

By means of the invention, it is possible to mount members <b>70</b> to the middle portion <b>18</b><i>m </i>prior to inserting the middle portion in the fuselage. In particular, it is possible to insert the middle portion after the fuselage segment has itself had its top portion closed. Mounting systems associated with the various portions of the floor prior to inserting the floor itself serves to reduce pollution generated by such mounting for all of the systems (in particular as a result of drilling operations). Similarly, mounting systems prior to inserting the floor makes mounting operations more ergonomic. The middle portion is fastened to the lateral portions in a zone of the fuselage that is relatively accessible such that putting rivets into place does not raise ergonomic problems.

The embodiment described above enables the middle portion <b>18</b><i>m </i>to be fitted relative to the lateral portions <b>18</b><i>l </i>in each of the directions Y and Z. In addition, the subassemblies formed by each batten-and-post pair present a certain amount of flexibility in the direction X, thus making it possible to fasten the middle portion <b>18</b><i>m </i>without running the risk of significantly deforming it if there is a problem with tolerances.

A second embodiment of the invention is shown in <figref idrefs="DRAWINGS">FIGS. 9 to 11</figref>. Elements that are not described again below are identical to elements of the above-described embodiment.

The battens <b>24</b> and the crossmembers <b>20</b> are once more channel-section members. Nevertheless, they are now fastened together back-to-back such that in this embodiment the outside faces of these two section members are in contact with each other. Likewise in this embodiment, the two channel-section members are generally of the same shape and of the same dimensions such that the top and bottom edges of the section members are coplanar, as shown in <figref idrefs="DRAWINGS">FIG. 11</figref>. Fastening is provided by rivets passing through the two overlapping walls in the direction X.

In this embodiment, the posts <b>26</b> are cylindrical in shape. Each post <b>26</b> is connected via its top and bottom ends to a lug in the form of a fitting <b>36</b> by means of a hinge about an axis <b>38</b> parallel to the direction X. The bottom fitting is rigidly fastened to the frame <b>12</b>, while the top fitting is rigidly fastened to the bottom of the crossmember or to the bottom of the batten, or indeed to the bottom of both of them, by means of a horizontal plate <b>40</b>. Once more, one of the rails <b>22</b> extends in register with the zone where the batten is fastened to the crossmember, and where these members are fastened to the post. The rail has its bottom face bearing against the top edge of the batten and of the crossmember. Nevertheless, it is not fastened directly thereto.

As in the above-described embodiment, this fastening technique provides degrees of freedom in the directions Y and Z so as to enable the position of the middle portion to be adjusted relative to the lateral portions. The way in which the airplane is assembled is the same as in the preceding embodiment.

A third embodiment of the embodiment is shown in <figref idrefs="DRAWINGS">FIGS. 12 to 16</figref>.

This time, the battens <b>24</b> are I section members except at their outer ends where they present only a plane web perpendicular to the direction X and coming into area contact against the plane wall of the frame <b>12</b>. Each of the crossmembers <b>20</b> also presents a I section. The shape and the dimensions of this section are the same as those of the section of the batten. Each batten is rigidly fastened to the crossmember by extending in line therewith. For this purpose, the inside end of the batten and the end of the crossmember have their bottom edges resting on the fitting <b>36</b> of the post <b>26</b>, to which they are fastened by means of rivets. Similarly and as previously stated, the rail <b>22</b> rests on the top edges of the batten and of the crossmember, to which it is directly fastened by means of rivets. It is solely by means of this fitting and this rail that the fastening is provided in this embodiment between the batten and the crossmember, with no direct fastening being provided between them. Fastening takes place via the horizontal flanges of the batten and of the crossmember. The rivets extend in a vertical direction. As can be seen in <figref idrefs="DRAWINGS">FIG. 16</figref>, the rail <b>22</b> presents a plurality of enlarged zones <b>42</b> in its base constituting plates that come into contact with each of the battens and the corresponding crossmember, respectively. Each plate provides a larger area for receiving rivets. As can be seen in <figref idrefs="DRAWINGS">FIG. 14</figref>, the wall of the crossmember in this location once more presents a greater thickness E than it does at its end, in the present example at its top and bottom edges, so as to reinforce it where it is fastened to the rails and to the posts.

Once more, this embodiment enables the position of the parts to be adjusted in the directions X and Y.

There follows a description of an aircraft in a fourth embodiment of the invention, with reference to <figref idrefs="DRAWINGS">FIGS. 17 to 26</figref>.

There follows a detailed description of the middle portion <b>58</b><i>m</i>, which in this embodiment does not have rails. Each crossmember <b>60</b> has a top partial crossmember <b>60</b><i>s </i>and a bottom partial crossmember <b>60</b><i>i</i>. Specifically, each of the partial crossmembers is a half-crossmember insofar as it constitutes substantially a bottom or a top half of the crossmember.

The bottom half-crossmember <b>601</b> presents a flange <b>67</b> forming its horizontal base and a vertical wall extending in a plane that is parallel to the directions Y and Z. The wall presents tongues <b>64</b> of generally triangular shape that extend it locally upwards. Specifically, there are five tongues in this example that are regularly spaced apart from one another along the half-crossmember. The top crossmember <b>60</b><i>s </i>presents an analogous arrangement with tongues <b>64</b> that extend downwards. The tongues of the top wall and of the bottom wall are located in the vicinity of one another so that their free ends overlap. In each overlap zone, one of which is shown in detail in <figref idrefs="DRAWINGS">FIG. 20</figref>, there is received a hinge pin <b>66</b> serving to fasten the top half-crossmember to the bottom half-crossmember by hinging together each pair of tongues <b>64</b>. The pin extends parallel to the direction X. As shown in <figref idrefs="DRAWINGS">FIG. 20</figref>, in the present example, the tongues of the bottom partial crossmember penetrate into the hollowed-out free ends of the tongues of the top partial crossmember. Nevertheless, in a variant embodiment, as shown in <figref idrefs="DRAWINGS">FIG. 21</figref>, provision may be made for the top and bottom tongues merely to overlap in the direction X. By means of the hinge connections via the tongues between the partial crossmembers making up each crossmember, the two partial crossmembers of each crossmember are rigidly fastened together.

The partial crossmembers of each crossmember <b>60</b> define gaps <b>68</b> between consecutive pairs of tongues <b>64</b>. In this example, there are six gaps <b>68</b> in each crossmember <b>60</b>.

Given that the crossmembers <b>60</b> are mutually identical and arranged to coincide, the gaps <b>68</b> likewise coincide from one crossmember to the next. This defines elongate housings in the direction X that are defined above by the partial crossmembers <b>60</b><i>s </i>and below by the partial crossmembers <b>601</b>. These housings are used to house systems or members <b>70</b> of the kind mentioned above that have functions other than a function relating to the floor. For example, they may be hydraulic or pneumatic members (compressed air or air conditioning ducts, water ducts, refrigeration ducts, oxygen ducts), electric cables, fire extinguisher circuit elements, or indeed ducts for on-board communications networks. The gaps <b>68</b> that follow one another along a crossmember may receive members of types that differ from one gap to another.

Furthermore, on each crossmember, the two partial crossmembers are fastened together at each of the crossmembers by means of a respective connection part <b>72</b> that is rigidly fastened to each of the partial crossmembers. The connection part is also hinged to the associated batten <b>74</b> about an axis <b>75</b> that is parallel to the direction X. The hinge pins between the connection parts <b>72</b> and the battens are preferably situated on the neutral axis in bending of the crossmembers <b>60</b>. The same applies for the pins <b>66</b>.

The floor also comprises a top panel <b>76</b> resting on the top partial crossmembers <b>60</b><i>s</i>. Rails <b>22</b>, two rails in this example, extending parallel to the direction X, are also provided in each lateral portion <b>58</b><i>l </i>of the floor. Each rail rests on one or more battens. The lateral ends of the panel rest on each of the rails <b>22</b>. The floor also has a bottom panel <b>78</b> fastened to the base <b>67</b> of the bottom partial crossmembers <b>601</b>. The top panel <b>76</b> forms the bottom limit of the airplane cabin <b>80</b>, while the bottom panel <b>78</b> forms the top limit of the airplane cargo zone <b>82</b>.

There follows a description of an implementation of the method of the invention for making and installing the airplane floor.

With reference to <figref idrefs="DRAWINGS">FIG. 22</figref>, in order to fabricate the floor, the top partial crossmembers <b>60</b><i>s </i>are initially fastened to the top panel <b>76</b> in their final positions underneath it.

The bottom partial crossmembers <b>601</b> are also temporarily fastened on an assembly jig <b>79</b> in the final positions that they are to occupy relative to one another.

Thereafter, the arrangement shown in <figref idrefs="DRAWINGS">FIG. 22</figref> is made by interposing between the members <b>70</b> that are to be housed in the gaps <b>68</b> between the subassembly of the panel <b>76</b> with the top partial crossmembers <b>60</b><i>s </i>on top and the subassembly of the jig <b>79</b> with the bottom partial crossmembers <b>601</b> underneath. The members <b>70</b> are also placed in the positions they are to occupy relative to one another.

Thereafter, all of these elements are moved towards one another in the vertical direction so as to form stack with the members <b>70</b> sandwiched between the two subassemblies. During this approach, the top partial crossmembers come into contact with the corresponding bottom partial crossmembers so as to form the crossmembers <b>60</b>, and the gaps <b>68</b> are formed around the members <b>70</b> which are thus received therein.

The assembly jig <b>79</b> presents openings or hatches enabling one or more operators to put the hinge pins <b>66</b> into place whereby the tongues <b>64</b> of the top and bottom crossmembers are connected together. This ensures that the top partial crossmembers are rigidly fastened to the bottom partial crossmembers.

Thereafter, the bottom partial crossmembers may be separated from the jig <b>79</b> and moved away therefrom.

Thereafter, the fastener parts <b>72</b> are put into place and then the bottom panel <b>78</b> is put into place.

The middle portion of the floor <b>58</b><i>m </i>as made up in this way and as shown in <figref idrefs="DRAWINGS">FIG. 23</figref> is then ready to be inserted into the destination fuselage segment.

Furthermore, the lateral floor portions <b>58</b><i>l </i>have already been mounted in this segment where they rest on the posts <b>26</b>. Likewise, certain systems <b>70</b> analogous to the system <b>70</b> have already been put into place, in particular in the “triangular” zones defined on top by the battens <b>74</b> and laterally by the frames <b>12</b> and by the posts <b>26</b>. Since the middle portion of the floor has not yet been installed at this stage, these members <b>70</b> can be put into place in a manner that is relatively comfortable for the operators.

It should be observed at this point that the middle portion of the floor <b>58</b><i>m </i>may be built up while the lateral portions <b>58</b><i>l </i>are being mounted in the fuselage and the systems <b>70</b> are being installed. These operations may therefore be performed in parallel (or simultaneously) in order to reduce the overall time taken to build the aircraft.

With reference to <figref idrefs="DRAWINGS">FIG. 23</figref>, the middle portion <b>58</b><i>m </i>is inserted in the fuselage segment. At this stage, the segment may already have its top portion closed, as shown in the figure, with insertion then taking place along the horizontal direction X. Once the middle portion has been received in position in register with the lateral portions <b>58</b><i>l</i>, it is fastened thereto by means of fasteners <b>72</b>. This fastening may be performed at this stage without performing any drilling operations, where such operations are considered as being polluting for the members situated in the environment in which they are performed.

In a variant, provision may be made during construction of the middle portion <b>58</b><i>m </i>to constitute the bottom subassembly with the bottom partial crossmembers <b>60</b><i>i </i>and the bottom panel <b>78</b> for the purpose of making the sandwich, rather than using an assembly jig. Under such circumstances, one or more access hatches are provided through the bottom panel <b>78</b> so as to allow the pins <b>66</b> to be put into place.

Provision could also be made to replace such hinges with mutual engagements that fasten the top partial crossmembers to the bottom partial crossmembers as soon as they are positioned relative to one another in their final relative position.

For example, the middle portion may have a total height of 182 millimeters (mm). The gaps <b>68</b> may have a height of 100 mm, for example.

With reference to <figref idrefs="DRAWINGS">FIG. 17</figref>, the airplane <b>2</b> has a plurality of rows of passenger seats <b>84</b>. The rows are parallel to the direction Y and they are disposed one behind another. In the present example, the airplane has a central aisle <b>86</b> intersecting the vertical longitudinal midplane of the fuselage. Specifically, each row has the same number of seats on either side of the aisle. In this example, there are three seats on the left and three seats on the right. The seats <b>84</b> in a row are mutually identical. Each of them has a seat back <b>88</b> and a seat proper <b>90</b>.

With reference to <figref idrefs="DRAWINGS">FIG. 24</figref>, the seats of the row are associated with respective supports <b>92</b>₁, <b>92</b>₂, and <b>92</b>₃, each support fully supporting the corresponding seat. For convenience, the seats of the row corresponding to the respective supports <b>92</b>₁, <b>92</b>₂, and <b>92</b>₃are given respective references, going from the aisle, of <b>84</b>₁, <b>84</b>₂, and <b>84</b>₃. Each support is formed by a rectangular frame extending in a horizontal plane. A seat is fastened via its seat proper to the corresponding support. In each row, the three supports <b>92</b>₁, <b>92</b>₂, and <b>92</b>₃for the seats situated on one side of the aisle constitute a single part or base <b>94</b>. The base comprises two spars <b>96</b> extending in the direction Y and four ribs <b>98</b> extending in the direction X. The two end ribs are located at the ends of the spars. The other two ribs are disposed respectively one-third and two-thirds of the way along them. Each support is defined by two of the ribs and by portions of both spars.

The base <b>94</b> is connected to the floor independently of the fuselage via a single leg <b>100</b> that is rigidly fastened to the base and that extends in a plane parallel to the directions X and Y. The leg extends at the junction between the two supports <b>92</b>₂and <b>92</b>₃that are the closest to the fuselage and the furthest from the aisle <b>86</b>. The leg <b>100</b> extends in register with the rib <b>98</b> common to the supports <b>92</b>₂and <b>92</b>₃. The leg <b>100</b> comprises three vertical uprights <b>102</b> and two ribs <b>104</b> that are inclined relative to the vertical direction. The leg <b>100</b> defines a front leg zone and a rear leg zone via each of which it bears directly on the floor. The leg is fastened directly to the rail <b>22</b> that bears on the battens <b>74</b>. In this example, the leg lies in the same vertical plane as the posts <b>26</b> supporting the ends of the battens.

Two braces <b>106</b> and <b>108</b> connect the supports <b>92</b> to the bottom portion of the leg <b>100</b>. One of the braces <b>106</b> extends from the rib <b>98</b> closest to the fuselage down to the leg. The other brace <b>108</b> extends from the rib <b>98</b> situated at the junction between the supports <b>92</b>₁and <b>92</b>₂down to the leg. Each of the braces is connected to the other parts via its ends by means of respective hinge connections about pins <b>107</b> parallel to the axis X. Both braces <b>106</b> and <b>108</b> extend in a common plane perpendicular to the direction X and situated halfway between the two spars <b>96</b>.

The base is also fastened to the fuselage via a rail <b>110</b> parallel to the direction x and fastened directly to a plurality of the frames <b>12</b>, being situated level with the base, the rail extending the base in the direction Y. Specifically, the base <b>94</b> is hinged to the rail <b>110</b> about a vertical pin <b>112</b>.

It can thus be seen that the support <b>92</b>₁of the seat adjacent to the aisle <b>86</b> is connected to the fuselage solely via the support <b>92</b>₂of the adjacent seat in the row. In other words, it is the support <b>92</b>₂that provides the entire support for the support <b>92</b>₁and its seat <b>84</b>₁. The seats <b>84</b>₁and <b>84</b>₂are supported together in a cantilevered configuration. Independently of the hinge fastening to the fuselage, all three seats and their supports are supported by the floor via the single leg <b>100</b>.

Such an arrangement serves to release the middle zone of the floor <b>58</b><i>m </i>from the loads that are transmitted by the seats. This is already advantageous when the floor is made as a single piece. However, in the present configuration, it can be understood that the entire middle portion <b>58</b><i>m </i>of the floor is relieved of any load transmitted by the seats, in particular in the event of a crash. Fastening the seat to the fuselage via the floor takes place only in the lateral portions <b>58</b><i>l</i>. There is thus no need to provide means in the middle portion for taking up the forces transmitted by the seats.

In addition, in the event of a crash, the loads generated by the seats are transmitted directly by the leg to the posts <b>26</b> and to the frames <b>12</b>. At the end of the row remote from the aisle, transmission via the rail <b>110</b> also takes place directly to the frames <b>12</b>.

In addition, fastening the middle portion <b>58</b><i>m </i>to the lateral portion <b>58</b><i>l </i>remains particularly simple since there is no need to fasten the middle portion to the seats, or vice versa.

<figref idrefs="DRAWINGS">FIG. 25</figref> illustrates a situation in which a force G, e.g. of magnitude equal to six times gravity, is applied in the vertical direction downwards on the support <b>92</b>₂. This stimulates the force transmitted via the seats by the passengers in the event of the airplane impacting the ground vertically. This force acts above the plane of the support <b>92</b>₂. This force is balanced: <ul><li id="ul0007-0001" num="0000"><ul><li id="ul0008-0001" num="0113">firstly by an upward vertical reaction RA transmitted by the fuselage to the leg <b>100</b>, and more precisely two vertical reactions RA/2 transmitted to the ends of the leg; and</li><li id="ul0008-0002" num="0114">secondly by a downward vertical reaction RB transmitted by the rail <b>110</b> to the end of the base.</li></ul></li></ul>

<figref idrefs="DRAWINGS">FIG. 26</figref> illustrates another situation in which a force G, e.g. of magnitude equal to nine times gravity, is applied in the forward horizontal direction to the same point as in the preceding figure. This simulates a front impact.

This force gives rise to two reactions RA/2 at both bottom ends of the leg <b>100</b>. Each of these reactions extends in the vertical plane of the leg and comprises a horizontal component extending rearwards and a vertical component extending upwards at the front and downwards at the rear. The force G also gives rise to a forward horizontal reaction RB transmitted by the rail <b>110</b> to the end of the base. In the absence of the hinge pin <b>112</b>, reaction forces from the rail <b>110</b> to the base <b>94</b> would appear that extend in the direction Y. Fastening the base rigidly to the rail would, on impact, give rise to a bending moment about a vertical axis. Unfortunately, in the presence of an assembly that is highly statically undetermined, such stresses are difficult to quantify, thereby complicate the design of the parts. The hinge makes the assembly isostatic in a horizontal plane and therefore simplifies design. Nevertheless, this hinge is optional.

In all of the embodiments, the floor rests on the fuselage firstly via its lateral ends and secondly via the posts that serve to take up vertical forces. In each embodiment, the arrangement of the floor provides good takeup of crash forces in each of the directions X, Y, and Z. In addition, the middle portion is fastened to the lateral portions without excessive stress and in a manner that enables the parts to be well-matched.

The parts constituting the fuselage, the floor, and the seat supports may be made of metal.

Naturally, numerous modifications may be applied to the invention without going beyond the ambit thereof.

Independently of the invention, provision may be made to fasten members to the floor prior to fitting all or part of the floor to the fuselage.

Provision could be made so that only the seat located at the end of the row is cantilevered out.

Provision could be made for it to be the top partial crossmembers <b>60</b><i>s </i>that are fastened to an assembly jig on a temporary basis. Similarly, provision could be made for the access hatch(es) to be provided in the top panel <b>76</b>.

It is possible to implement the characteristic relating to the seat adjacent to the aisle being supported by being connected to the fuselage solely via the support of the adjacent seat in the row, without the middle portion of the floor necessarily being made using partial crossmembers. By way of example, the middle portion may have crossmembers each constituted as a single piece, and longitudinal rails fastened rigidly to the crossmembers as in the first three embodiments.